There is currently no convenient and sensitive clinical indicator of vascular damage. Angiotensin-converting enzyme may provide this indicator since it exists on the surface of endothelial cells and is processed and released into the blood. A measure of released cellular enzyme may provide a direct estiamte of vascular damage. This work would provide a method for separation and quantitation of both forms in the circulation and constitute a new diagnostic tool and give new insights into the etiology of poorly understood vascular disease states. First, I propose to implement recently reported affinity chromatography methods for the rapid purification of angiotensin- converting enzyme from human serum, tissue homogenates, cultured endothelial cells, and culture medium. Second, separation of isozymes will be accomplished by techniques that are based on known or expected differences in charge and lectin binding characteristics of cell and serum associated forms. These methods include non denaturing polyacrylamide and high resolution agarose gel electrophoresis, isoelectric focusing, and chromatofocusing, while lectin bining based methods include inhibition, affinity, chromatography, and lectin gel electrophoresis. Pilot studies will check for correlation of enzyme forms with a number of disease states, including sarcoidosis, psoriasis, silicosis, respiratory distress syndrome-both adult and neonatal, diabetes mellitus, all of which are reported to demonstrate altered levels of this enzyme activity, as well as atherosclerosis and other disease states in which vascular damage is implicated.